The conventional liquid-cooled internal combustion engine relies primarily on axial flow fans to draw cooling air from outside of the vehicle through the liquid-to-air heat exchanger or radiator for cooling. Various efforts have been made to improve cooling, including increasing the liquid capacity of the radiator, increasing the size or number of fan blades, and changing the pitch of the fan blades.
Complicating the challenge of efficiently cooling the liquid-cooled internal combustion engine is the fact that engine undergoes air flow and temperature changes during operation. When the vehicle is moving, particularly at highway speed, air cooling is elevated and the coolant temperature is lowered. However, when the vehicle is operating in stop-and-go conditions or when the vehicle is standing still, the effectiveness of air cooling drops considerably because the volume of air passing through the radiator is diminished.
In some instances vehicle designers have introduced fan shrouds to assure that there is sufficient cooling air passing through the radiator to reduce the temperature of the radiator coolant to thereby improve cooling efficiency in idle or near-idle conditions. A shroud directed to this purpose is intended to improve the air suction generated by the fan.
The shapes of known fan shrouds have traditionally been determined only by packaging demands that are themselves determined by increasingly restrictive engine compartments. Given such limitations and the lack of understanding about the dynamics of air flow, the influence of known shrouds on the airflow has been negligible.
As in so many areas of vehicle technology, there is always room for improvement related to the cooling arrangements for liquid-cooled internal combustion engines.